1. Field of the Invention
This invention relates broadly to cellular wireless communication networks. More particularly, this invention relates to a methodology and systems for identification and measurement of interference in such cellular wireless communication networks.
2. State of the Art
Because cellular wireless communication networks re-use frequency across geographic areas, all cellular wireless communication networks contain interference (both co-channel and adjacent channel). Wireless protocols (AMPS, IS-136, CDMA, WCDMA, GSM . . . ) all take this into consideration. However, it is important for network carriers to manage interference to its minimum possible levels because interference within a network reduces capacity (the number of subscribers, or amount of data, a network can accommodate). Thus, to maximize the amount of revenue a network can generate and to minimize the capital expenditures necessary to support that revenue (i.e. purchasing new base stations), it is critical that the network interference be minimized.
The current solutions for optimizing cellular wireless telephone networks involve a process of gathering network data and processing that data to determine the best possible optimization of network variables to minimize interference. The data can come from a number of sources, but drive testing is the most accurate. Drive testing is the process of driving the roads in a given market with a piece of test equipment that typically includes a laptop computer integrated with a wireless handset, a GPS receiver and a demodulating scanning receiver. Once the drive test data is collected, the data is typically provided to post-processing tools which apply various mathematical algorithms to the data to accomplish network planning and optimization. An example of post-processing is automatic frequency planning (AFP), where the data is processed to determine the optimal arrangement of frequencies to cell site sectors to minimize network interference. Another post-processing application is automatic cell planning (ACP) which analyzes network variables to aid network engineers in making decisions on how best to minimize interference in the network. These network variables include: the frequencies (for FDMA networks) or pilot numbers (for CDMA networks) per cell site sector, the cell site antenna's height and/or angle, the cell site sector's transmission power, cell site locations or new cell site locations, and a host of other variables that impact radio frequency propagation.
The problem with the current methodologies is that the drive-test data is all collected at ground level, creating a two-dimensional data set. This data is then processed to minimize interference for a two-dimensional model. However, because many users of the wireless communication network are not at ground level, but rather above ground level in buildings, these “optimized” solutions fail to account for above ground level usage. This is particularly true for urban environments.